No longer run automated tests on node 0.6

"node 0.6 is not supported officially any more since some time" - has
been causing errors for us of this sort:
https://github.com/npm/npm/issues/4391
Merge pull request #133 from leapmotion/node-test-versions

No longer run automated tests on node 0.6
Merge branch 'master' into node-focus